I had the opportunity to ask this basic question to a maltster that produces the base malt for Budweiser. She was one of only a few people in the world with a PHD in malting. So know that is her bias-- big technology, lots of data and testing, and scientific background rather then traditional processes and the art of hands on craft brewing.
Paraphrasing her--
* Barley grown in different places and malted differently is different and will taste different. Her malt is specifically made to Budweisers criteria using state of art technology in a very controlled process. She says she knows enough to know that there is plenty she doesn't know. Many things they do-- they do because it gets the results they desire, confirmed by testing, but they do not necessarily know why. For instance all malt when finished-- is aged a certain amount of time before selling. She did not know why this is necessary but she knows that is necessary and problems will result if this is not done. Aging/storing malt costs them money and they not do it if they could get away with it.
* What one brewer wants may be different then what another brewer wants. And malting techniques vary immensely!
* All malt changes from season to season. So brands change in flavor.
* All malts have vastly benefited from the big breweries investing vast amounts of money perfecting the art/science of breeding barley and malting.
* All malt 100 or even 25 years ago is vastly inferior by any measure to malt today.
* Organic malt is poor malt because they have to sell high percentages of malt they would normally throw away because oraganic barley is so inconsistent and poor quality from nature of the organic farming of barley. So avoid organic malt. Sorry greenies-- i happen to agree-- never had an organic beer i particularly liked.
* I asked her about Marris Otter- because I like it-- but she said floor malting is both impossible to do on a large scale and produces a malt that would never be acceptable for her standards. I could go into that but there is no sense to. In the same conversation she said if you like that malt-- then by all means use it-- but that malt was inferior by her standards though. (I still use the malt and love it when i can afford it-- i consider it not better or worse just different-- probably won't try it in a lager though)
Anyway to keep this brief use malt that is meant for your style of beer unless you are experimenting.
You'll never get a straight answer about which malt to use or if they are interchangeable from anyone-- even if they know more about the topic then anyone else alive.
For me that makes the hobby even more fun! There is no 'right' answer to which malt or any other ingredient to use and leaves us open to a lot of possibilities-- to make amazing beer! (and you'll only know the secret
)
Instead of thinking of malt as an ingredient think of it as part of your brewing procedure. Barley goes from plant to beer and maltsters and brewers help that happen. Brewers pick up where maltsters leave off. Pick a malt/maltster that works with the style/origin of the beer you are making unless you are experimenting. For example that's not to say you can't use American malts-- base and specialty-- in a Belgian beer... But the result will simply be different because the malts ARE DIFFERENT. How much different? Probably varies...